A bane of existence for many tradesman is separation of screw head or other fastener from a screwdriver tip or other bit during screw installation. Many tools use magnetization to hold a tool bit and a fastener together during driving operations. A typical arrangement is where a magnet is positioned near to or at the driving end of a screw driver's shank. The magnet imparts a magnetization to the tool bit which in turn attracts a ferrous fastener, such as a metal screw. The magnet is often lodged in a socket or a chuck at the tip of the shank; see for instance, U.S. Pat. No. 5,941,139 (Vodehnal); U.S. Pat. No. 5,913,596 (Lin); and U.S. Pat. No. 5,603,248 (Eggert et. al).
These designs have the disadvantage of being expensive to produce and cumbersome to use, especially in tight places. Moreover, the device must be discarded as a whole (magnet, bit, and handle) when, after repeated usage, the magnet loses its strength. Finally, typical tool configurations do not capture a major fraction of the magnetization force of the magnet.
Another design is where a magnetic ring or donut with a circular inner bore is slidably received by the tool shank and positioned at a point intermediate between the handle of the tool and the socket or chuck at the driving end. Such a design is disclosed in U.S. Pat. No. 5,861,789 (Bundy et al.) where a magnetic ring with a circular inside bore is slid over the working end of a screw driver to come to rest along the shank of the tool. This arrangement is cumbersome and bulky inasmuch as it requires the rink to be positioned precisely along a tool shank to confer magnetization to the bit. The ring is also positioned proximal to the handle and intermediate the handle and the bit. As a result of this positioning, full strength of the magnet is seldom available to effect the tool bit or the fastener driven by the bit.
Thus, there is a need in the art for a magnetic bit- or fastener- or nut-holding device that is both compact and economical to produce and to use. The device should utilize the full strength of a magnet to hold the bit and/or a fastener or a nut at the tip of the bit. The device should also provide mechanical means for imparting torque to the bit and/or to the fastener.